(a) Technical Field
The present disclosure relates to a method for manufacturing a high temperature resistant sound absorbing material for vehicles, which includes mixing a fiber material having a limiting oxygen index (LOI) of about 25% or higher and a heat resistant temperature of about 200° C. or higher with a thermosetting binder resin having a heat resistant temperature of about 200° C. or higher. The high temperature resistant sound absorbing material may maintain a substantially consistent shape at a high temperature of about 200° C. or higher and complies with flame retardant standards of Underwriters Laboratories (UL) 94V-0Thus, the material may be used as an automobile part to reduce noise generated in an engine and an exhaust system and may improve automotive N.V.H. (noise, vibration and harshness).
(b) Background Art
While a vehicle is in motion, various types of noises are generated. Automobile noise is generally divided into two types depending on a noise source, an engine or an exhaust system. The noises generated from the engine and exhaust system are delivered to the interior of a vehicle. To reduce the noises generated from the engine and exhaust system and delivered to the interior of a vehicle, a sound absorbing material for vehicles has been developed. In particular, insulation dash and a dash isolation pad are used to prevent engine radiated noise from being emitted into the interior of a vehicle, and a tunnel pad and a floor carpet are used to prevent noises generated from the exhaust system and the bottom of a motor vehicle from being emitted into the interior of the vehicle.
Recently developed methods for manufacturing a sound absorbing material include the steps of: inserting a synthetic resin film layer having a thickness of about 40 to 100 μm between pet fiber layers having a thickness of about 20 mm; passing the pet fiber layers into which the synthetic resin film layer is inserted through a preheating chamber; and compressing the pet fiber layers to create a thickness of about 20 mm. In addition, recently developed methods include a method for producing a sound absorbing material, including the steps of; cutting a polyester fiber and an acrylic fiber; beating the polyester fiber and the acrylic fiber to separate the fibers; mixing the fibers with a low melting point polyester fiber and carding; molding; heating to melt the low melting point polyester fiber to make nonwoven fabric form; compressing and cooling; and cutting the fabric to a desired shape. Further, another recently developed method discloses coating at least one of the top and bottom layers of polyester (PET) felt with a mixture fiber including a low melting fiber (LMF).
The recently developed sound absorbing materials however, increase the weight of the material to sufficiently reduce the noises radiated from the engine and exhaust system. However, the effectiveness of sound proofing is insufficient compared to the increased weight of the material. To overcome these limitations, a sound absorbing material must be applied close to the noise source such as an engine or an exhaust system. To accomplish such placement, the sound absorbing material be capable of maintaining a substantially consistent shape under high temperature conditions such as about 200° C. or higher and must exhibit flame retardant properties. Thus, the conventional sound absorbing materials cannot be used for this purpose
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.